1. Field of the Invention
The present invention relates to rock crushers having a drive mechanism for moving a movable jaw between a pair of fixed jaws.
2. Description of the Prior Art
It is preferable in movable jaw type rock crushers to have the jaw move as nearly lineally as possible between a pair of stationary jaws. This is because the greatest crushing efficiency is achieved by linear motion of one jaw relative to the other, in contrast to orbital motion. Furthermore, because most crushing takes place between the lower ends of the movable and fixed jaws, it is particularly desirable that the motion of the jaw be substantially linear in that region.
Heretofore, drive mechanisms employing a single cam have been utilized to impart motion to the movable jaw of a crusher. However, as typified by U.S. Pat. No. 2,737,349, such mechanisms commonly impart an orbital motion to the movable jaw. Consequently, the efficiency of such devices in crushing materials is impaired. Furthermore, such crushers often utilize mechanical links either for supporting the movable jaw or as part of the drive mechanism. Due to the unusually high stresses associated with rock crushing operations, mechanical links of this type are subject to wear and breakage. When this occurs, the crusher is often inoperative for a substantial period of time, at great cost and lost productivity, while repairs are made.
In another known type crusher, as exemplified by U.S. Pat. Nos. 2,177,524 and 2,487,744, a complex revolving cam drive assembly slides against friction or wear pads during at least a portion of rotation of the cam. During each revolution of the cam, a portion of the motion of the cam, usually a portion of the vertical component of its motion, is not transferred to the movable jaw. In addition to frequent time consuming replacement of worn out friction pads, more energy is required to drive such devices to overcome the friction between the drive mechanism and the pads.
Still another form of rock crusher is illustrated in U.S. Pat. No. 3,145,938. The drive mechanism of this prior art device includes an eccentric positioned toward the top of a movable jaw. A mechanical link coupled between the framework of the crusher and a lower portion of the jaw slides relative to a pin on the jaw. Because of this sliding motion, a portion of the vertical component of motion that would be otherwise imparted to the jaw by the eccentric is lost. Although the lower portion of the movable jaw of this device apparently moves back and forth along a line approximately 45.degree. from horizontal, the motion of the upper and mid portions of the jaw is orbital as in other prior art crushers. Also, such a crusher suffers from the disadvantages associated with devices having mechanical links in that these links are subject to failure. Furthermore, sliding mechanical links of this type tend to rapidly wear, particularly when grit produced during crushing lodges between the sliding link and pin.
U.S. Pat. No. 2,505,132 discloses still another rock crusher utilizing an eccentric cam type drive mechanism. This device utilizes a link 28 to transmit motion from the drive mechanism to the movable jaw and hence suffers from the drawbacks mentioned above.
Therefore, a need exists for a relatively trouble free and mechanically simple rock crusher having a drive mechanism capable of imparting substantially linear motion to a movable jaw between a pair of fixed jaws.